a. Field of the Invention
This invention relates to vehicle brakes. In particular, the invention relates to a drum brake assembly and method for designing a drum brake assembly in which a camshaft of the drum brake assembly is configured to reduce audible noise during braking.
b. Background Art
In a conventional drum brake, a drum rotates with a wheel or wheels proximate to one end of an axle. The drum defines a radially inner braking surface. A brake spider is disposed about the axle and a pair of brake shoes are pivotally mounted at one end to the brake spider. The opposite end of each brake shoe is engaged by an actuating member such as a cam to move the brake shoes between positions of engagement and disengagement with the braking surface of the brake drum.
Some drum brakes emit a long, high-pitched noise or squeal (e.g., a single tone noise within the audible range of humans typically between 60 and 120 decibels) during application of the brakes when the brake shoes engage the braking surface of the drum. This noise is unpleasant and distracting to the driver of the vehicle from which the noise emanates and to others within the audible range of the noise including drivers in surrounding vehicles. The noise can also result in warranty claims by vehicle owners asserting that the brake is not functioning properly.
The inventor herein has recognized a need for a drum brake assembly and a method of designing a drum brake assembly that will reduce one or more of the above-identified deficiencies and/or provide improved performance.